Defroster for refrigerator evaporators



D 8, 1953 D. J. LANKER Q 2,661,602

DEFROSTER FOR REFRIGERATOR EVAPORATORS F-iled July 5, 1951 2 Sheets-Sheet 1 INVENTOR.

OQ/VAZD d. JAN/(3? Dec. 8, 1953 D. J. LANKER DEFROSTER FOR REFRIGERATOR EVAPORATORS 2 Sheets-Sheet 2 Filed Jilly 5, 1951 e w MA V A m. J 0 M M 0 ATTORNEYS Patented Dec. 8, 1953 UNITED STATES PATENT OFFICE DEFROSTER FOR REFRIGERATOR EVAPORATORS Donald J. Lanker, Lima, Ohio, assignor to Artkraft Manufacturing Corporation, Lima, Ohio a corporation of Ohio 6 Claims.

This invention relates to defrosting of refrigerator evaporators and in particular to the automatic defrosting of refrigerator evaporators.

It is an object of this invention to produce a defrosting mechanism for the evaporator of a refrigeration system which is efficient in operation, of simple structure, and which can be readily adapted to any refrigeration system without altering the system.

This invention also contemplates a defroster of the above type which is dependable and substantially free of service trouble.

The present invention contemplates a method and arrangement for defrosting a refrigerator evaporator which utilizes hot gaseous refrigerant in the system to defrost the evaporator during the normal operation or refrigerating cycle of the refrigerating system.

In the drawings:

Fig. 1 shows a mechanical refrigeration system provided with the defrosting mechanism which is the subject of this invention, and in Fig. l the evaporator is shown in rear elevation.

Fig. 2 is a detail showing the heating element positioned within a coil of the refrigerant conducting tube.

Fig. 3 is an electric circuit diagram showing the defrosting mechanism connected into the electrical circuit for the refrigerating system.

Fig. 4 is a horizontal section through the evaporator taken along the line 4-4 of Fig. 1.

Fig. 5 is a detail sectional view of one of the evaporator plates along the line 5-5 of Fig. 4.

Fig. 6 is a section along the line 66 of Fig. 4.

Referring more particularly to the drawings there is shown for purposes of illustration a mechanical refrigeration system of conventional design comprising a motor compressor 1, a condenser 2 connected by a capillary restrictor tube 3 with an evaporator 4. The return suction or low pressure line from the evaporator to the comressor is designated 5.

The evaporator, for purposes of illustration, is shown as a three plate type comprising lower plate 6, center plate I and top plate 8. Each plate comprises an upper sheet 9 and a lower sheet I of aluminum or other high heat conducting metal which are riveted to each other and to the side wall ll of the evaporator by rivets I2 (Fig. The capillary restrictor tube 3 connects into a larger metal tube I3 which is sandwiched between plates =9 and In in each of the shelves 6, 1 and 8 and extends back and forth within the plates as shown in Fig. 4. From the uppermost plate the refrigerant passes into an accumulator dryer M which connects into the suction line '5.

The evaporator tube I3 is formed into a helical coil l5 just preceding the point at which the tube [3 enters the lower plate 6. The evaporator tube 53 is also shaped into the form of a helical coil l6 where it runs from the outlet ll of lower plate 6 to the inlet I 8 of middle plate 1. Evaporator tube 13 is also formed into a helical coil l9 where it runs from the outlet 20 of middle plate 1 to the inlet 2| of top plate 8. The helical or spiral coils I5, I 6 and IQ of the tube l3 facilitate mounting of the heating elements 22 in heat exchange relation with the refrigerant in the system. Whatever the form the evaporator may take, the important point is that of heating the gaseous refrigerant while it is passing through the evaporator.

Capillary tube 3 is shown only by way of example as one known means for separating the high compression side of the refrigeration system from the low compression or suction side and since the refrigerant passes into the low pressure side of the system upon entering tube I 3, it is understood that the tube l3 and coils I5, l6 and I9 form a portion of the evaporator the same as the portion of the tube [3 within each of the plates 6, 1 and 8 although, of course, the main refrigeration effect is produced in plates 6, I and 8.

Since it is proposed to heat the refrigerant within the evaporator during the normal cycling of the refrigeration system, that is, while the compressor is running, electrical heating elements 22 are mounted within each of the coils l5, l6 and I9 in heat exchange relation therewith. Each electrical resistance. heating element 22 is of a conventional type and consists of a stainless steel sheath 23 in which is housed the electrical resistance element or wire 24 and insulated from the sheath by magnesium oxide 25 or other suitable insulator. The leads to each of the heating elements 22 are designated 26 and 21.

The electrical circuit diagram is shown in Fig. 3. TM designates a conventional timing motor which is connected with a volt source of electricity LI and L2. C is the thermostatically operated cold control switch 22. TMI and TM2 are switches which are opened and closed by timer motor TM. Each of the heating elements 22 is connected in parallel into the 110 volt electrical system LI and L2 and are controlled by a timer motor switch TMI. For purposes of illustration, there is shown a heating element 22 for each of the coils l5, l6 and is. If desired, a heating element can be provided only for coil I ahead of bottom plate 5 but the provision of additional heating elements in coils l6 and i 9 expedites the defrosting operation.

The operation of thedefrosting mechanism is as follows: When the cold control switch C is closed and calling for refrigeration, then motor compressor unit I is opened and the refrigerant flows from motor compressor l into condenser 2 and thence through capillary tube 3 and into the spiral coil l5, then through plate 6,.coil 16, plate 1, coil l9, and upper plate BJinto: the-accumulator M and thence through line 5 back to the intake side of the compressor. This. is a conventional refrigeration cycle.

The timing motor is set so that after the refrigerator has operated "any selected period of timesuch, for example, as twelve ortwenty-four hours, the, timing motor TM will close timer switches TMI and TMZ and electrical current will now flow through each of the resistance heating elements 22 and the motor compressor unit. will be set in operation irrespective of whether cold control switch C is closed oropen. The timing device TM, TMl, TMZ is set so that it will cut on the electric current through the heating elements 22 and motor compressor unit [for aselected period of timesuch, for example, as eight to ten minutes.

It is important thatthe compressor i should be running while the current isflowing through theheating elements 22 so that the heating eifect of the elements 22 will be quickly transmitted throughout the evaporator and melt the frost thereon. The heating element 22 in lower coil [5, which is preferably the main heating element having thelargest wattage, say, for example, 300 to 400 watts, overcomes the refrigeration effect of the refrigerant within the coil and starts warming the refrigerant flowing through the bottom plate. The resistance element 22 within coil l6 has a lower wattage, say, for example, about 200 watts, and the heating element within coil I9 has a lower Wattage of say, for example, about 100 watts. The heating element 22 within the coil l6 further warms up the refrigerant so that it does not condense in this coil H5 or in middle plate '1. The heating element within the third coil l9 also heats up the refrigerant further so that it will not condense in the coil H! or in the topplate 8. The heat transmittedfrom the heating elements 22 to the refrigerant is in turn transmitted: through the walls of the evaporator to the frost on theevaporator and quickly melts this frost. At the end of the defrosting cycle, timer motor switch TM, TMI, 1M2 opens, cutting off the current through the timer motor switch to motor compressor unit I and heating elements 22. The operation of the refrigeration system is now controlled by the thermostatic cold control switch C.

The heating elements 22 slide into the coils l5, l6 and I9 and can be removed very readily. Preferably the heating elements 22 contact the insides of coils l5, l6 and I9 around the entire circumference and have a snug fit therein. The heating elements 22 are all located on or in the low pressure side of the refrigeration system. If the heating elements 22'are removed, the refrigerator operates in anormal manner without any defrosting cycle.

From. the above it is evident that the instant 4 defrosting mechanism defrosts the evaporator by heating the refrigerant within the system and utilizing the refrigerant as the medium for conducting or transmitting heat from an outside heating source to the evaporator and thence to the frost on the evaporator. In effect, the instant defrosting mechanism converts the evaporator into a'radiator'and-the refrigerant into a heat transmitting medium during the defrosting cycle without in anywise altering the normal refrigerating operation or cycle of the refrigeration system.

The temperature to which the heating elements 22;rise:;can be varied... A safe temperature limit for the'heating elements 22 is from to F., 'butthe temperature of the heating elements will vary with the capacity of the evaporator.

If desired the timer TM, TMi can control the heating elements 22 only and the thermostatically operated cold control switch C can be used to 7 turn on. the refrigeration mechanismor motor compressor. It iszonly necessary that-the motor compressor should runsimultaneously with the energization of .the heating element or. elements 22 but it is not necessary tdstartand stop the motor compressor. simultaneously with theenerization and deenergizationwof heating elements 22. In .other words, itisnot necessaryin Fig. 3 that switches 'IMi and TMZ closeor open simul taneously, it is only necessary that they both should be closed during sufficient and overlapping periods of time to defrost the refrigerator. The heating elements .22 put more heat into the refrigerant than the refrigerant can absorb as it evaporates. The heating means '(22') should be positioned in the low side of the systemand a part or all of the heating means shouldbe positioned adjacent the expansion means (capillary tube or expansion valve) that is, adj a'cent'the point'where the high side connects into the low side,'so that all frostwill'be removed from the low'side.

I claim:

1. In a refrigeration system of'the' type including an evaporator, a condenser, a fluid line connecting the condenser and'the evaporator, and a restrictor in the fluid line-between the condenser and evaporator, the fluid line leading intothe evaporator from the restrictor being in the form of a helical coil, an electric motor driven compressor for compressing the refrigerant and circulating the refrigerant through the system and an electrical circuitfor supplyingcurrent to said motor, a heating element positioned within said coil and in heat exchange relation therewith, a switch adapted to'be connected into'saicl electrical circuit to supply current-simultaneouslyto said motor for'running the same and current tosaid heating element to heat the same, saidheater having sufiicient capacity 'to convert the liquid refrigerant into'a warm vapor Wherebythe heater overcomes the refrigerationeffectand warms the gaseous refrigerant flowing through the evaporator sufliciently to defrost theevaporator.

2. The combination defined in claim .1 wherein the evaporator comprisesa pluralityof plates and the refrigerant lines leading to saidv plates from said restrictortake the formof helicalcoils and wherein .the heating elements are positioned within said helical :coils.

. 3. In a refrigeratingtsystem including anevaporator and an electricrmotor' driven compressor for compressing and-circulating the refrigerant through the.system,;adefrosting:mechanismcomprising a helical tubular: coil inzthelow side of'the systemthrough which-therefrigerant passesyand a heating element positioned in said coil in heat exchange relation therewith for heating the refrigerant flowing through said coil, said heating element giving sufficient heat to the refrigerant to vaporize the refrigerant and overcome the refrigeration efiect of such vaporization whereby to cause warm vapor to flow through the evaporator to thereby defrost the evaporator.

4. The combination defined in claim 3 including timer switch means adapted to be connected into the electrical circuits of said heating element and electric motor for closing the circuits through said motor and heating element at selected intervals of time and for a selected period of time and the heating element supplies heat to the re frigerant during the defrosting cycle.

5. In a refrigerating system including an evap= orator and an electric motor driven compressor for compressing and circulating the refrigerant through the system, a defrosting mechanism comprising a helical tubular coil in the low side of the system through which the refrigerant passes, and a heating element positioned in said coil in heat exchange relation therewith for heating the refrigerant flowing through said coil, said heating element giving sufficient heat to the refrigerant to vaporize the refrigerant and overcome the refrigeration efiect of the vaporized refrigerant as it passes through the evaporator to thereby defrost the evaporator, said heating element hav- References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 882,224 Williams Mar. 17, 1908 1,913,433 Doble June 13, 1933 2,001,323 Dick May 14, 1935 2,086,622 Kagi July 13, 1937 2,095,014 Stark Oct. 5, 1937 2,313,390 Newton Mar. 7, 1943 2,459,173 McCloy Jan. 18, 1949 2,492,397 Peterson Dec. 27, 1949 2,573,684 Binder Nov. 6, 1951 2,595,967 McCloy May 6, 1952 2,598,408 McCloy May 27, 1952 2,616,272 McCloy Nov. 4, 1952 FOREIGN PATENTS Number Country Date Switzerland Sept. 2, 1940 

